1-Bromopropane based fluids have found widespread use in industry for solvent cleaning, i.e. vapor degreasing, cold cleaning and ultrasonic cleaning of complex metal parts, circuit boards, electronic components, implantable prosthetic devices, optical equipment and others.
In its simplest form, vapor degreasing or solvent cleaning consists of exposing a room temperature object to be cleaned to the vapors of a boiling solvent. Vapors condensing on the object provide clean distilled solvent to wash away grease or other contaminants. Final evaporation of the solvent from the object leaves no residue on the object.
For difficult to remove soils where elevated temperature is necessary to improve the cleaning action of the solvent, or for large volume assembly line operations where the cleaning of metal parts and assemblies must be done efficiently, a vapor degreaser is employed. The conventional operation of a vapor degreaser consists of immersing the part to be cleaned in a sump of boiling solvent which removes the bulk of the soil, thereafter immersing the part in a sump containing freshly distilled solvent near room temperature, and finally exposing the part to solvent vapors over the boiling sump which condense on the cleaned part. The part can also be sprayed with distilled solvent before final rinsing.
Azeotropic or azeotrope-like compositions are particularly desired because they do not fractionate upon boiling. This behavior is desirable because in the previously described vapor degreasing equipment in which these solvents are employed, redistilled material is generated for final rinse-cleaning. Thus, the vapor degreasing system acts as a still. Unless the solvent composition exhibits a constant boiling point, i.e., is azeotrope-like, fractionation will occur and undesirable solvent distribution may act to upset the cleaning and safety of processing.
The art is continually seeking new solvent mixtures which offer alternatives for the above-described applications. Currently, environmentally acceptable materials are of particular interest because the traditionally used fully halogenated chlorocarbons and chlorofluorocarbons have been implicated in causing environmental problems associated with the depletion of the earth's protective ozone layer. Mathematical models have substantiated that 1-bromopropane will not adversely affect atmospheric chemistry because its contribution to stratospheric ozone depletion and global warming in comparison to the fully halogenated chlorocarbons and chlorofluorocarbons species is negligible. The ozone depletion potential of 1-bromopropane is 0.002-0.03, which is significantly lower than the ozone depletion potentials of 1,1,2-trichloro-1,2,2-trifluoroethane or CFC-113 (0.8) and 1,1-dichloro-1-fluoroethane or HCFC-141 b (0.11). The global warming potential of 1-bromopropane (0.31) is also significantly lower than CFC-113 (5000) and HCFC-141b (630).
The art has also looked to compositions which include components which contribute additionally desired characteristics, such as polar functionality, increased solvency power, and stabilizers while retaining those properties exhibited by the prior art chlorofluorocarbons including chemical stability, low toxicity, and non-flammability.
It is accordingly an object of this invention to provide novel ternary compositions based on 1-bromopropane, nitromethane or acetonitrile and at least one alcohol, and preferably azeotrope-like compositions, which are useful in solvent and other applications and which meet the above criteria.
The present compositions are advantageous for the following reasons. The 1-bromopropane component has an ozone depletion potential of 0.002-0.03 and has reasonable solvency characteristics. The alcohol has good solvent properties to enable the cleaning and dissolution of ionics, flux resin and oils. The nitromethane or acetonitrile component is known to inhibit the decomposition of 1-bromopropane. Thus, when these components are combined in effective amounts, an efficient, stable, environmentally acceptable solvent composition results.